Mr Ballinger was working with the crewing company that was responsible for the rigging and staging.

“The number that I have in my head from that show was 10,500 people in the beer garden. And I’ve heard numbers that are 14,000 or higher,” he said.

“That was definitely one of the craziest gigs I have ever worked on. I have still not seen anything like it. It was nuts.”

Not only was the venue pushed well beyond capacity, Mr Ballinger said there were some very real dangers.

“When the guys turned up to the show they had a look at the stage, which was made of scaffolding which was then tied in to the crowd barrier at the front.

“They took one look and said ‘This isn’t going to work. The barrier needs to be separated from the stage so if the barrier goes it doesn’t take the stage with it.

“The staging guy said ‘Mate, I’ve been setting up concerts in this country for 20 years so don’t come in here telling me how to do my job’.”

The response from the band?

“You’ve never seen anything like a Nirvana crowd.”

“So it was changed,” Mr Ballinger said. “And I’m glad it was because it was 10,500 people going absolutely nuts.”

Nirvana’s album Nevermind was not initially pegged by its record company as a possible hit record. It went on to sell more than 30 million copies worldwide.

Neither was the tour expected to draw massive crowds.

“I remember as we were setting up, one of the older guys said ‘Who’s this Nirvana band?’ Being a young uni student I was more in tune, listening to Triple J, and I said ‘It’s a sound like you’ve never heard before’,” Mr Ballinger said.

“One of the guys slapped their leg laughing when they started playing and said ‘They’re bloody awful!’

The thousands at Fishos disagreed, and the show — along with the entire Australian tour — has been recounted time and again as the beginning of a significant change in Australian music.

Smells Like Teen Spirit, the opening track on Nevermind, is often hailed as the point where alternative rock entered the mainstream.

Amongst it all, lead singer and guitarist Kurt Cobain struggled with heroin addiction, illness and depression.

He took his own life two years later on April 8, 1994.

His struggles with drug use were already well documented, and it was something that Mr Ballinger said he saw first hand.

“It was a brutally hot day that day on the Gold Coast, and I remember I was looking for a drink and someone said ‘Oh, just go into that American band’s trailer there, they’ve got a whole rubbish bin full of cold drinks’,” Mr Ballinger recalled.

“This must have been half an hour, if that, from when Nirvana had come offstage, and I walked in to the bus and there was Kurt Cobain laid out in the aisle of the bus, I understand having had a big hit of heroin after he’d come offstage.

“He could have been a one-hit wonder at that point. No-one could have known that Nirvana would become that big.”